Condition of 'if' expression is constant: report enum entries comparison

#KT-28803 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/ConstantConditionIfInspection.kt

@@ -14,7 +14,11 @@ import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.isElseIf
 import org.jetbrains.kotlin.idea.intentions.branchedTransformations.unwrapBlockOrParenthesis
+import org.jetbrains.kotlin.idea.references.mainReference
+import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.containingClass
+import org.jetbrains.kotlin.psi.psiUtil.getChildrenOfType
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.BindingContext
@@ -116,12 +120,42 @@ class ConstantConditionIfInspection : AbstractKotlinInspection() {
 private fun KtIfExpression.branch(thenBranch: Boolean) = if (thenBranch) then else `else`
 
 private fun KtExpression.constantBooleanValue(context: BindingContext): Boolean? {
+    val enumEntriesComparison = enumEntriesComparison()
+    if (enumEntriesComparison != null) {
+        return enumEntriesComparison
+    }
     val type = getType(context) ?: return null
-
     val constantValue = ConstantExpressionEvaluator.getConstant(this, context)?.toConstantValue(type)
     return constantValue?.value as? Boolean
 }
 
+private fun KtExpression.enumEntriesComparison(): Boolean? {
+    if (this !is KtBinaryExpression) return null
+    val leftEnumEntry = left?.enumEntry() ?: return null
+    val rightEnumEntry = right?.enumEntry() ?: return null
+
+    val leftEnum = leftEnumEntry.containingClass() ?: return null
+    val rightEnum = rightEnumEntry.containingClass() ?: return null
+    if (leftEnum != rightEnum) return null
+
+    val enumEntries = leftEnum.body?.getChildrenOfType<KtEnumEntry>() ?: return null
+    val leftIndex = enumEntries.indexOf(leftEnumEntry)
+    val rightIndex = enumEntries.indexOf(rightEnumEntry)
+    return when (operationToken) {
+        KtTokens.EQEQ -> leftIndex == rightIndex
+        KtTokens.GT -> leftIndex > rightIndex
+        KtTokens.GTEQ -> leftIndex >= rightIndex
+        KtTokens.LT -> leftIndex < rightIndex
+        KtTokens.LTEQ -> leftIndex <= rightIndex
+        KtTokens.EXCLEQ -> leftIndex != rightIndex
+        else -> null
+    }
+}
+
+private fun KtExpression.enumEntry(): KtEnumEntry? {
+    return ((this as? KtDotQualifiedExpression)?.selectorExpression ?: this).mainReference?.resolve() as? KtEnumEntry
+}
+
 fun KtExpression.replaceWithBranch(branch: KtExpression, isUsedAsExpression: Boolean, keepBraces: Boolean = false) {
     val lastExpression = when {
         branch !is KtBlockExpression -> replaced(branch)

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.A == Enum.A) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq2.1.kt

@@ -0,0 +1,5 @@
+package test
+
+enum class Enum {
+    A, B, C
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq2.1.kt.after

@@ -0,0 +1,5 @@
+package test
+
+enum class Enum {
+    A, B, C
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq2.kt

@@ -0,0 +1,6 @@
+// PROBLEM: Condition is always 'true'
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>test.Enum.A == test.Enum.A) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq2.kt.after

@@ -0,0 +1,6 @@
+// PROBLEM: Condition is always 'true'
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq3.1.kt

@@ -0,0 +1,5 @@
+package test
+
+enum class Enum {
+    A, B, C
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq3.1.kt.after

@@ -0,0 +1,5 @@
+package test
+
+enum class Enum {
+    A, B, C
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq3.kt

@@ -0,0 +1,8 @@
+// PROBLEM: Condition is always 'true'
+import test.Enum.*
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>A == A) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq3.kt.after

@@ -0,0 +1,8 @@
+// PROBLEM: Condition is always 'true'
+import test.Enum.*
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryGt.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.B > Enum.A) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryGt.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryGtEq.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.B >= Enum.A) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryGtEq.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryGtEq2.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.B >= Enum.B) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryGtEq2.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryLt.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.B < Enum.C) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryLt.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryLtEq.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.B <= Enum.C) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryLtEq.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryLtEq2.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.B <= Enum.B) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryLtEq2.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'true'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(1)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryNotEq.kt

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'false'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(if (<caret>Enum.A != Enum.A) 1 else 2)
+}

idea/testData/inspectionsLocal/constantConditionIf/enumEntryNotEq.kt.after

@@ -0,0 +1,10 @@
+// PROBLEM: Condition is always 'false'
+enum class Enum {
+    A, B, C
+}
+
+fun foo(x: Int) {}
+
+fun bar() {
+    foo(2)
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -1524,6 +1524,56 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/constantConditionIf/endWithElseIfNoBraces.kt");
         }
 
+        @TestMetadata("enumEntryEq.kt")
+        public void testEnumEntryEq() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq.kt");
+        }
+
+        @TestMetadata("enumEntryEq2.kt")
+        public void testEnumEntryEq2() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq2.kt");
+        }
+
+        @TestMetadata("enumEntryEq3.kt")
+        public void testEnumEntryEq3() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryEq3.kt");
+        }
+
+        @TestMetadata("enumEntryGt.kt")
+        public void testEnumEntryGt() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryGt.kt");
+        }
+
+        @TestMetadata("enumEntryGtEq.kt")
+        public void testEnumEntryGtEq() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryGtEq.kt");
+        }
+
+        @TestMetadata("enumEntryGtEq2.kt")
+        public void testEnumEntryGtEq2() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryGtEq2.kt");
+        }
+
+        @TestMetadata("enumEntryLt.kt")
+        public void testEnumEntryLt() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryLt.kt");
+        }
+
+        @TestMetadata("enumEntryLtEq.kt")
+        public void testEnumEntryLtEq() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryLtEq.kt");
+        }
+
+        @TestMetadata("enumEntryLtEq2.kt")
+        public void testEnumEntryLtEq2() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryLtEq2.kt");
+        }
+
+        @TestMetadata("enumEntryNotEq.kt")
+        public void testEnumEntryNotEq() throws Exception {
+            runTest("idea/testData/inspectionsLocal/constantConditionIf/enumEntryNotEq.kt");
+        }
+
         @TestMetadata("expression.kt")
         public void testExpression() throws Exception {
             runTest("idea/testData/inspectionsLocal/constantConditionIf/expression.kt");